Use of alkanolamines based on propylene oxide as additives in lubricants

ABSTRACT

A lubricant which comprises an alkanolamine of the formula I 
     
       
         
         
             
             
         
       
     
     of the formula II 
     
       
         
         
             
             
         
       
     
     of the formula III 
     
       
         
         
             
             
         
       
     
     of the formula IV 
     
       
         
         
             
             
         
       
     
     or a mixture of alkanolamines selected from alkanolamines of the formulae I to IV, 
     where R1, R2, R3, R1′, R2′ and R3′ are each independently a hydrogen atom or a C1 to C4 alkyl group, and R 4  is a C1 to C16 alkyl group.

The present application incorporates the provisional U.S. Application61/410,000 filed Nov. 4, 2010 by reference.

The invention relates to lubricants which comprise an alkanolamine ofthe formula I

of the formula II

of the formula III

of the formula IV

or a mixture of alkanolamines selected from alkanolamines of theformulae I to IV, where R1, R2, R3, R1′, R2′ and R3′ are eachindependently a hydrogen atom or a C1 to C4 alkyl group, and R⁴ is a C1to C16 alkyl group.

Lubricants, especially also what are known as cooling lubricants, areused in the manufacturing industry to reduce friction and simultaneouslyto remove heat. Cooling lubricants are used in machine tools in order tobe able to produce a maximum number of workpieces with high quality.

Lubricants, especially cooling lubricants, comprise natural orsynthetic, i.e. modified, mineral oils as an essential constituent.

Frequently, aqueous lubricants are used. These are, for example, aqueoussolutions of polar synthetic or correspondingly polar-modified naturalmineral oils, or else aqueous emulsions in which the mineral oil hasbeen emulsified with the aid of a surface-active compound. In the caseof aqueous lubricants, there is the possibility of infestation withorganic microorganisms, such as fungi or bacteria. To counteract this,biocides are added. WO 2005/055720 discloses that specificalkylethanolamines can additionally inhibit bacterial growth.

DE-A 10 2008 043 580 describes alkanolamines which can be used asadditives to lubricants, have biocide-promoting action, regulate the pHand improve the emulsification of the mineral oil in aqueous lubricants.

What are desired are alternative additives to lubricants, with which theabove effects are fulfilled to a maximum degree with a minimum amountadded.

It was therefore an object of the present invention to providelubricants which have good performance properties and for that purposeneed contain a minimum level of simple additives. Furthermore, theadditives should be very easy to prepare and, optionally, should be ofminimum toxicological concern.

Accordingly, the lubricants defined at the outset have been found.

The inventive lubricants comprise an alkanolamine of the above formula I

of the formula II

of the formula III

of the formula IV

or a mixture of alkanolamines selected from alkanolamines of theformulae I to IV.

Preferably, R4 is a C1 to C8 alkyl group, especially a C1 to C4 alkylgroup and more preferably a methyl group or ethyl group.

In a preferred embodiment, R1 is identical to R1, R2 to R2′ and R3 toR3′. This is the result especially of the process for preparationdescribed below.

More particularly, R1 and R1′ are each a hydrogen atom.

In a preferred embodiment, R1 and R1′ are each a hydrogen atom, and atleast one of the R2 and R3 radicals and at least one of the R2′ and R3′radicals are each a hydrogen atom.

In particularly preferred embodiment, R1, R2, R3, R1, R2′ and R3′ areeach a hydrogen atom.

In a preferred embodiment, the alkanolamine is of the formula I or II,most preferably of the formula I.

A further embodiment concerns a mixture of alkanolamines selected fromalkanolamines of the formulae I to IV.

Such a mixture may, for example, comprise different alkanolamines of theformula I or consist exclusively of different alkanolamines of theformula I. The same applies to alkanolamines of the formulae II to IV.

The mixture preferably comprises alkanolamines of different formulae Ito IV; especially suitable are mixtures which comprise alkanolamines ofthe formula I.

In addition to an alkanolamine of the formula I, the mixture especiallyalso comprises an alkanolamine of the formula II and optionallyalkanolamines of the formulae III and IV.

Particular preference is given to a mixture which consists of analkanolamine of the formula I to an extent of more than 60% by weight,especially to an extent of more than 80% by weight.

Preferred alkanonolamines of the formula I are alkanolamines of theformula Ia:

Preferred alkanolamines of the formula II are alkanolamines of theformula IIa:

In the formulae Ia and IIa, R4 is as defined above.

Accordingly, a very particularly preferred mixture of alkanolamines is amixture which comprises alkanolamines of the formula Ia andalkanolamines of the formula IIa. More particularly, R⁴ in formulae Iaand IIa is identical.

Useful mixtures are especially those which consist to an extent of 50 to99% by weight, especially to an extent of 80 to 99% by weight, of analkanolamine of the formula I, especially of the formula Ia, andcorrespondingly to an extent of 1 to 50% by weight, especially to anextent of 1 to 20% by weight, of an alkanolamine of the formula II,especially of the formula IIa, and to an extent of 0 to 10% by weight ofalkanolamines of the formulae III and IV, where the percentages byweight are based on the total weight of the alkanolamines of theformulae I to IV.

The above alkanolamines can be prepared by customary processes. Thealkanolamines can be prepared especially by a two-stage addition ofprimary amines of the formula H₂N—R⁴ onto propylene oxide or propyleneoxide derivatives.

In the 1st stage, the primary amine can add onto the R², R³-substitutedcarbon atom of the propylene oxide or propylene oxide derivativeaccording to the schematic diagram below:

The primary amine can alternatively also add onto the CH₃-substitutedcarbon atom, so as to result in the structurally isomeric additionproduct below.

The product of the 1st stage is therefore generally a mixture of thesetwo addition products.

In the second stage, the secondary amine obtained again adds onto apropylene oxide or propylene oxide derivative; in the schematic diagrambelow, this is shown only by the example of one of the two additionproducts obtained in the 1st stage:

Again, it is possible for a mixture of two addition products to formhere, according to which carbon atom of the epoxy group the secondaryamine has added onto.

Preceding from the two addition products of the 1st stage, it is thusalso possible to obtain a mixture of alkanolamines of the formulae I toIV.

The mixture obtained can be used in accordance with the invention asdescribed above. However, it is also possible to remove a single desiredalkanolamine from the mixture and use it correspondingly in lubricants.

The lubricants comprise the alkanolamine or the mixture of alkanolaminespreferably in an amount of 0.05 to 30% by weight, more preferably of 0.1to 20% by weight and most preferably of 0.5 to 10% by weight, based onthe total amount of lubricant.

The alkanolamines can be added to the lubricant in any way at any timebefore or during use. The alkanolamines can be added directly to thelubricant which already comprises all further constituents; they canalso be mixed beforehand with other constituents of the lubricant andthen combined in this form with the remaining constituents of thelubricant. In one embodiment, in the case of aqueous lubricants (seebelow), it is possible first to prepare what are called lubricantconcentrates, i.e. compositions which already comprise the constituentsof the lubricant apart from the water. The latter is then added beforeuse to the lubricant concentrates in the amount so as to result in thedistribution desired for the particular use of the lubricant in theapparatus in which the lubricant is being employed.

Based on the lubricant concentrate in the case of aqueous lubricants,the total amount of the alkanolamines used in accordance with theinvention is preferably at least 2% by weight, most preferably at least5% by weight, based on the lubricant concentrate; the maximum amount ispreferably 30% by weight, especially 20% by weight, likewise based onthe lubricant concentrate.

The lubricants comprise, as an essential constituent, preferably anatural or synthetic lubricant component.

Natural lubricant components are, for example, mineral oils, i.e. oilswhich are obtained by distillation from brown coal, hard coal, peat,wood or especially mineral oil. They comprise especially saturatedhydrocarbons.

Synthetic lubricant components are, for example, oils which are producedfrom suitable starting materials or by chemical modification of naturalmineral oils (for example so-called ester oils).

Further types of lubricant components which can be used in the inventivelubricants are known to specialists in the art.

The lubricants are generally liquid under the use conditions (pressure,temperature). They are preferably liquid at 21° C., 1 bar.

A distinction is drawn between nonaqueous and aqueous lubricants. In thecontext of this invention, aqueous lubricants are preferred.

The aqueous lubricants may be aqueous solutions of correspondingly polarmineral oils, for example synthetic, polymeric alcohols.

The aqueous lubricants may also be emulsions of natural or syntheticmineral oils in water.

Aqueous lubricants may be marketed in the form of the solution oremulsion; another option is, however, that the solution or dispersion isnot prepared from the starting materials until just before the lateruse.

The inventive lubricants are preferably aqueous lubricants, especiallyaqueous solutions of mineral oils and more preferably aqueous emulsionsof mineral oils.

According to the requirement, the inventive lubricants may comprisefurther additives. Useful examples include additives for regulatingviscosity, additives for reducing corrosion, additives for reducing foamformation, additives for reducing friction, biocides, or else otheradditives for improving performance properties, especially thelubrication and heat removal.

The effect of this may be that, in addition to the inventivealkanolamine or alkanolamine mixtures of the formulae I to IV or othermixtures thereof, other amines are constituents of the correspondinglubricants or lubricant concentrates, and the efficacy of the latter isenhanced by an alkanolamine of the formulae I to IV or a mixture ofthese alkanolamines.

The mineral oil may be self-emulsifying in the aqueous emulsions, i.e.it is chemically modified such that an emulsion in water forms withoutfurther additives. The emulsions preferably comprise, however, asurface-active compound which brings about or contributes to theemulsification of the mineral oil. Useful compounds for this purpose arecustomary emulsifiers and/or protective colloids.

The inventive lubricants are especially cooling lubricants; the latternot only bring about good lubrication but also ensure good heat removal,for example during the processing or production of workpieces in machinetools.

The inventive lubricants or cooling lubricants can be used in anydesired fields of manufacturing technology. They are suitable formachine tools of all kinds. They have particular significance, forexample, in the industrial manufacture of parts of tools or machines,and in particular of aircraft and vehicle components. In this context,the use of the inventive lubricants in the production of lightweightmetal components, for example made of magnesium and aluminum, isparticularly preferred.

A further field of use for the inventive lubricants or coolinglubricants involves use in conveying measures of all kinds (mining, oilextraction of all kinds). Here, for example, addition of the inventivelubricants prolongs the functioning and lifetime of the boring machine.

In addition, the inventive lubricants or cooling lubricants can be usedin transmissions or turbines, for example including vehicletransmissions or transmissions of wind turbines.

Alkanolamines of the formulae I to IV or mixtures thereof, regulate thepH and bring about corrosion protection.

It is an advantage of the inventive lubricants that the alkanolaminesadditionally contribute to emulsification of the mineral oil, and so itmay optionally even be possible to dispense with further surface-activecompounds.

Furthermore, the alkanolamines of the formulae I to IV and mixturesthereof promote the action of the biocide component, and thus theefficacy toward bacteria, for example mycobacterium, or toward fungi.

1. A lubricant which comprises an alkanolamine of the formula I

of the formula II

of the formula III

of the formula IV

or a mixture of alkanolamines selected from alkanolamines of the formulae I to IV, where R1, R2, R3, R1′, R2′ and R3′ are each independently a hydrogen atom or a C1 to C4 alkyl group, and R⁴ is a C1 to C16 alkyl group.
 2. The lubricant according to claim 1, wherein R4 is a C1 to C4 alkyl group.
 3. The lubricant according to claim 1 or 2, wherein R¹ is identical to R^(1′), R² to R^(2′), and R³ to R^(3′).
 4. The lubricant according to any of claims 1 to 3, wherein R1, R2, R3, R1′, R2′ and R3′ are each a hydrogen atom.
 5. The lubricant according to any of claims 1 to 4, which is a mixture of alkanolamines comprising alkanolamines of the formulae I and II.
 6. The lubricant according to any of claims 1 to 5, which is a mixture of alkanolamines consisting to an extent of at least 80% by weight of an alkanolamine of the formula I.
 7. The lubricant according to any of claims 1 to 6, which comprises the alkanolamine or the mixture of the alkanolamines in amounts of 0.05 to 30% by weight.
 8. The lubricant according to any of claims 1 to 7, which comprises aqueous lubricants.
 9. The lubricant according to any of claims 1 to 8, which comprises aqueous solutions or emulsions.
 10. The lubricant according to any of claims 1 to 9, which comprises aqueous solutions or emulsions of synthetic or nonsynthetic mineral oils.
 11. The lubricant according to any of claims 1 to 10, which comprises further additives selected from additives for adjusting viscosity, additives for reducing corrosion, additives for reducing foam formation, additives for reducing friction, biocides and optionally other additives for improving performance properties.
 12. The lubricant according to any of claims 1 to 11, which comprises cooling lubricants.
 13. The use of lubricants according to any of claims 1 to 11 as lubricants in the manufacture of components or in conveying activities.
 14. The use of lubricants according to any of claims 1 to 11 in transmissions or turbines. 